package com.hmdp.utils;


import cn.hutool.core.util.BooleanUtil;
import cn.hutool.core.util.StrUtil;
import cn.hutool.json.JSONObject;
import cn.hutool.json.JSONUtil;
import com.hmdp.entity.Shop;
import lombok.extern.slf4j.Slf4j;
import org.springframework.data.redis.core.StringRedisTemplate;
import org.springframework.stereotype.Component;
import org.yaml.snakeyaml.events.Event;

import javax.annotation.Resource;
import java.time.LocalDateTime;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.TimeUnit;
import java.util.function.Function;

import static com.hmdp.utils.RedisConstants.*;

@Slf4j
@Component
public class CacheClient {

    @Resource
    private StringRedisTemplate stringRedisTemplate;


    public void set(String key, Object value, Long time, TimeUnit unit) {
        stringRedisTemplate.opsForValue().set(key, JSONUtil.toJsonStr(value), time, unit);
    }


    public void setWithLogicalExpire(String key, Object value, Long time, TimeUnit unit) {
        RedisData redisData = new RedisData();
        redisData.setData(value);
        redisData.setExpireTime(LocalDateTime.now().plusSeconds(unit.toSeconds(time)));
        stringRedisTemplate.opsForValue().set(key, JSONUtil.toJsonStr(redisData));
    }


    public <R,ID>R queryWithPassThrough(
            String keyPrefix, ID id, Class<R> type, Function<ID,R> dbFallback,Long time, TimeUnit unit) {
        String key = keyPrefix + id;
        //1.从redis中查询店铺缓存
        String json = stringRedisTemplate.opsForValue().get(key);
        //2.判断是否存在
        if (StrUtil.isNotBlank(json)) {
            //3.存在之间返回
            return JSONUtil.toBean(json, type);
        }

        //判断命中的是否为空值
        if (json != null) {
            //到这里说是一个空值，返回一个错误信息
            return null;
        }

        //4.这里查缓存，没查到说明是null(redis中不存在这个数据)需要向数据库中查询，根据id查询数据库
        R r = dbFallback.apply(id);
        //5.如果数据库当中也没有，返回错误
        if (r== null) {
            //将空值写入redis(防止缓存击穿)
            stringRedisTemplate.opsForValue().set(key, "", CACHE_NULL_TTL, TimeUnit.MINUTES);
            return null;
        }
        //6.存在，先写入redis中
        this.set(key,r,time,unit);
        //7.返回店铺的信息。
        return r;
    }
    private static final ExecutorService CACHE_REBUILD_EXECUTOR= Executors.newFixedThreadPool(10);

    public <R,ID> R queryWithLogicalExpire(String keyPrefix, ID id, Class<R> type, Function<ID,R> dbFallback,Long time, TimeUnit unit) {
        String key= keyPrefix + id;
        //1.从redis中查询店铺缓存
        String json = stringRedisTemplate.opsForValue().get(key);
        //2.判断是否命中
        if (StrUtil.isBlank(json)) {
            //3.未命中直接返回
            return null;
        }
        //4.命中。需要先把json反序列化为对象
        RedisData redisData = JSONUtil.toBean(json, RedisData.class);
        R r=JSONUtil.toBean((JSONObject) redisData.getData(),type);
        LocalDateTime expireTime = redisData.getExpireTime();
        //5.判断是否过期(这里过期指的是我们自己设置的逻辑过期)
        if (expireTime.isAfter(LocalDateTime.now())){
            //5.1.未过期，直接返回店铺信息
            return r;
        }
        //5.2.过期，需要缓存重建
        //6.缓存重建
        //6.1.尝试获取互斥锁
        String lockKey=LOCK_SHOP_KEY+id;
        boolean isLock = tryLock(lockKey);
        //6.2.判断互斥锁是否获取成功
        if (isLock){
            //6.3。成功，开启独立线程。实现缓存重建
            CACHE_REBUILD_EXECUTOR.submit(()->{
                try {
                    //查询数据库
                    R r1 = dbFallback.apply(id);
                    //写入redis
                    this.setWithLogicalExpire(key,r1,time,unit);
                } catch (Exception e) {
                    throw new RuntimeException(e);
                } finally {
                    //释放互斥锁
                    unlock(lockKey);
                }
            });
        }

        //6.4.返回商铺信息
        return r;
    }

    //尝试获取锁
    private boolean tryLock(String key){
        Boolean flag = stringRedisTemplate.opsForValue().setIfAbsent(key, "1", 10, TimeUnit.SECONDS);
        return BooleanUtil.isTrue(flag);
    }

    private void unlock(String key){
        stringRedisTemplate.delete(key);
    }


}
